We propose to develop a tandem mass spectrometer in which both MS1 and MS2 are time-of-flight (TOF) mass analyzers. Each mass analyzer will combine pulsed and delayed ion extraction with reflection focusing. Pulsed extraction will provide space focusing as well as permitting relaxation of metastable ions, which constitute the major limitation in resolution for high mass ions. Energy focusing will be provided by the reflectron, with a spatially focused beam of stable molecular and fragment ions as its input. The design will be a versatile one in that the ion source, both reflectron flight regions, and the collision chamber can be electrically floated from 0 to =/-6kV. this will enable us to compare and evaluate high energy collision induced dissociation (CID), low energy CID, and endothermic ion molecule reactions schemes for producing product ion (sequence) spectra as to both efficiency and focusing (mass resolution). Einsel lens focusing and quadrupole steering will provide a compact beam to enable the use of a relatively short flight tube and large reflectron angle, while maintaining excellent reflectron focusing. For high energy collisions, both deep reflectrons and product ion reacceleration will be examined for their focusing capabilities. Decelleration lenses, with high focusing, will be used to inject ions into the collision chamber at the very low energies needed for endothermic reactions. In the case of beam energy is consumed in the formation of the product ions, so that these ions at rest will be reaccelerated by pulsed ion extraction. The aim of the project is to produce an optimal configuration for the rapid analysis of tryptic (and other enzymatic) digests of proteins, when combined with high performance liquid chromatography (HPLC). The high repetition rate of the TOF analyzer, combined with high speed integrated transient recording developed in our laboratory, will enable us to obtain sequence information (in real time) from both separated and co-eluting peptides.